Boots – shoes – and leggings
Patent
1996-08-26
1998-11-24
Voeltz, Emanuel Todd
Boots, shoes, and leggings
364554, 364582, G06F 1718
Patent
active
058416676
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to methods and apparatus for evaluating the performance of complex signal processing devices and systems, particularly those which incorporate or make use of non-linear processes and which are subject to unpredictable fluctuations in input signal quality. The devices and systems may have digital inputs and outputs (D-D), analogue inputs and outputs (A-A), analogue inputs and digital outputs (A-D) or digital inputs and analogue outputs (D-A).
Examples of such devices and systems are: modems (modulators and demodulators) which are generally A-D and D-A devices; codecs (data compression and decompression devices) which may be D-D or A-A; encryptors and de-encryptors, digital error correcting systems and digital switching systems (usually D-D); signal equalisers, space-diversity signal combiners, IF-equalisers and various other signal distortion-correcting means (usually A-A); A-D and D-A converters; systems used in the recording and playing-back signals (such as analogue or digital magnetic tape systems and magnetic or optical disc systems) and systems for transmitting and receiving signals over a data or telecommunications medium (which may be any of the four species). Indeed, the principles of this invention can also be applied to the evaluation of some forms of transducers which can be regarded as signal-processing devices.
This invention may be used for the rapid, qualitative and quantitative comparison of the performance of a test signal-processing device with a similar reference device, or for determining whether and to what degree the performance of a given device has degraded over time (by comparing current performance with a record of earlier performance). Thus, the methods and apparatus of the invention are suited to the calibration of complex signal-processing devices against reference standards for the purpose of meeting device performance specifications.
While the most important and beneficial applications of this invention will be in the evaluation of signal-processing devices with non-linear characteristics (ie, those for which accurate transfer functions normally cannot be derived), its use is not confined to such complex systems as it may also be used in the assessment of nominallylinear systems and devices.
BACKGROUND TO THE INVENTION
Evaluating the performance of complex DSP (digital signal-processing) devices for the purpose of calibration or reliability assessment, or for checking performance-drift over time, can be a time consuming task. For example, modern 16 and 256 QAM (quadrature amplitude modulated) modems are expected to have symbol error rate probabilities (Pe) of better than about 24.5 and 34.7 dB respectively). Many modems claim a Pe of better than 10.sup.-14, taking into account the combined effects of noise, distortion and modem calibration error. To meet such specifications, modem manufacturers must calibrate each modem by lengthy trial-and-error measurement and adjustment procedures. This cannot be done, for example, by simply adjusting voltages, currents, carrier phase, decision thresholds and the like parameters to their design values (or to the same values measured in a reference modem), for such modems include non-linear sub-systems (eg, signal equalisers, digital error-correctors, and discriminators).
If the performance specifications of a 16 QAM modem require a BER (bit error ratio) better than 1:10.sup.-12 when input S/N is 24.5 dB, there is little alternative but to generate and apply a test signal with that S/N to the modem being calibrated, count the output errors and adjust the calibration variables by trial and error until the specification is met. Because very low error rates are involved, calibration can take a long time so that the calibration of a high-performance modem can represent a significant proportion of the cost of the device. The situation is even more onerous where (as is now common) high-performance modems are claimed to be tolerant to rapid multipath fading, group delay and other forms of input signal dis
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Derwent Abstract Accession No. 94-073361/09, Class S01, RU, A, 2002372, (Voron Communication Inst.), Oct. 30, 1985.
Figure 6.28, "Digital Line of Sight Radio Links: A Handbook", by Townsend, published by Prentice Hall in (1988).
Martin Communications Pty Ltd.
Smithers Matthew
Todd Voeltz Emanuel
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